Method and apparatus for providing an alert with information signal between a mobile switching center and a base station

ABSTRACT

The invention is a method and apparatus for providing an Alert With Information Message signal between a mobile switching center and a base station in a cellular communication system. The invention recognizes that current provisions of the IS-634 standard lack support for certain required functionality on the interface between a mobile switching center and a base station, or the A-Interface. An Alert With Information Message signal is introduced on the A-Interface to support the required functionality. Introduction of the Alert With Information Message provides support for reliable call processing on the A-Interface for the call waiting procedure, the hard handoff procedure, and the resolution of a glare condition.

This application claims the benefit of Provisional Application No.60/040,319, filed Feb. 14, 1997.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to spread spectrum telecommunicationssystems. More particularly, the present invention relates to a novel andimproved messaging method and apparatus in a CDMA communication system.

II. Description of the Related Art

The use of code division multiple access (CDMA) modulation techniques isone of several techniques for facilitating communications in which alarge number of system users are present. Although other techniques suchas time division multiple access (TDMA), frequency division multipleaccess (FDMA), and amplitude modulation (AM) schemes such as amplitudecompanded single sideband (ACSSB) are known, CDMA has significantadvantages over these other techniques. The use of CDMA techniques in amultiple access communication system is disclosed in U.S. Pat. No.4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATIONSYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” assigned to theassignee of the present invention and incorporated by reference herein.

In the CDMA cellular system, a large number of mobile telephone systemusers, each having a transceiver, communicates through satelliterepeaters or terrestrial stations which are also referred to as cells.Each cell includes a physical plant called a base station. A cell coversa limited geographic area and routes calls carried over cellulartelephones to and from a telecommunication network via a mobileswitching center. When a cellular telephone user moves into thegeographic area of a new cell, the routing of that user's call may beeventually made through the new cell by a process called a “handoff”.

A cellular telephone or, more specifically, a mobile station, broadcastsa signal that is received by a base station. The signal is then relayedto a mobile switching center which in turn routes the signal to thepublic switched telephone network and to telephone lines or other mobilestations. Similarly, a signal may be transmitted from the publicswitched telephone network to a mobile station via a base station and amobile switching center. The communications channel allocated forcommunication of information between the mobile station and the basestation is called the traffic channel.

The interface between the mobile station and the base station isreferred to as the Air-Interface. The telecommunications industryassociation (TIA) has provided a standard for CDMA call processing onthe Air-Interface entitled “IS-95-A Mobile Station—Base StationCompatibility Standard for Dual Mode Wideband Spread Spectrum CellularSystem,” hereinafter IS-95-A, which is incorporated by reference. Theinterface between the base station and the mobile switching center isreferred to as the A-Interface. The TIA has provided for call processingon the A-Interface through the standard provided in “IS-634 MobileSwitching Center—Base Station Interface for Public 800 MHz,” which isalso incorporated by reference. IS-95-A and IS-634 both define themessages and signals that are sent on their respective interfaces forthe operation of a CDMA cellular telephone call.

The call flow in a CDMA environment requires processing on both theAir-Interface and the A-Interface. The successful progression of a callrequires that the proper messages and signals are sent at the righttimes on both the Air-Interface and the A-Interface. The IS-634 standardis being developed to provide for call processing on the A-Interface. Anumber of problems and deficiencies are present in IS-634 whichcurrently does not support some of the necessary operations on theA-Interface. Some of these problems and deficiencies are recognized andsolved by the present invention in the manner described below.

SUMMARY OF THE INVENTION

The present invention is a novel and improved method and apparatus forproviding a new message on the interface between a mobile switchingcenter and a base station, also known as the A-Interface, of a cellulartelephone system. The present invention recognizes that the A-Interface,as presently defined by the IS-634 standard, does not support some ofthe operations necessary for reliable call processing. Introduction ofthe new message will provide support for required functionality on theA-Interface.

The present invention recognizes that improvements are needed for theA-Interface to reliably handle the call waiting and the hard handoffprocedures. In addition, a better technique is needed for resolving aglare condition. An Alert With Information Message is introduced on theA-Interface to improve the operation of these procedures.

Using the call waiting feature, a mobile station may have a first partyof a public switched telephone network put on hold while being connectedto a second party. If the second party hangs up, then according to thecurrent procedure, a Release/Clear Message (or an equivalent message) issent to the mobile station, causing the mobile station to release itstraffic channel. A new traffic channel must then be reestablished toreconnect the mobile with the first party. The present inventionrecognizes that the current procedure is unreliable in that difficultiesmay arise in the process of reconnecting the mobile with the firstparty. Moreover, Air-Interface resources are used inefficiently as thecurrent procedure requires the release of the traffic channel and thereassignment of a new channel. To overcome these shortcomings, an AlertWith Information Message is sent on the A-Interface to the base station,triggering the transmittal of an Alert With Information Message on theAir-Interface. Upon receipt of the Alert With Information Message, themobile station is prompted to transmit a Connect Message to the mobileswitching center via a base station. The mobile switching center thenreconnects the first party to the mobile station, without the need toreestablish a new traffic channel.

A hard handoff occurs in a cellular system when a mobile station movesfrom the coverage area of one base station to the coverage area ofanother base station. During a mobile station terminated call, in orderfor the mobile to undertake handoff, it must first receive an Alert WithInformation Message transmitted by the base station. Under currentprocedure, the Alert With Information Message is generated andtransmitted solely by the base station in whose coverage area the mobileis currently located. The present invention recognizes that the currentprocedure may cause the hard handoff procedure to be unreliable. If themobile moves from the coverage area of a first base station to thecoverage area of a second base station, the mobile station may neverreceive the Alert With Information Message from the first base station,resulting in a dropped call. Thus, the present invention provides for anAlert With Information Message to be generated and transmitted by themobile switching center. While the mobile station is moving from thecoverage area of the first base station to that of the second basestation, the mobile switching center transmits the Alert WithInformation Message to the second base station. The second base stationin turn transmits an Alert With Information Message to the mobilestation. Having received the Alert With Information Message, handoff cannow proceed without the call being dropped.

A mobile subscriber may attempt to originate a call while another partyis attempting to call the same mobile subscriber, resulting in a glarecondition. The Air-Interface standard, IS-95-A, provides the mobile theoption of aborting the call that it is originating and responding to thecall that it is receiving. However, the present invention recognizesthat the mobile may not successfully receive the call because the basestation is not configured to transmit the proper messages to the mobilewhen a glare condition occurs. In order for the mobile subscriber torespond to a call, it is necessary for the mobile to receive an AlertWith Information Message. However, the standard currently does notaddress this situation. As a result, the call may be dropped. Thepresent invention recognizes that the resolution of the glare conditionshould be undertaken at the mobile switching center. The mobileswitching center, upon receiving a message indicative of a mobileoriginating a call and subsequently receiving a message indicative ofthe same mobile receiving a call, should recognize that the mobile isproceeding with receiving a call. The mobile switching center shouldthen transmit an Alert With Information Message to the base station,triggering the base station to transmit an Alert With InformationMessage to the mobile station. As the Alert With Information Message isreceived by the mobile station, the glare condition is resolved withoutthe call being dropped.

Benefits and advantages of the present invention will become apparentfrom the following description of the preferred embodiment when it isconsidered with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 is a block diagram presenting a schematic overview of anexemplary CDMA cellular telephone system in accordance with the presentinvention;

FIG. 2 is a block diagram illustrating an exemplary call-waitingscenario according to the current IS-634 standard;

FIG. 3 is a block diagram illustrating a call-waiting scenario accordingto the present invention;

FIG. 4 is a flow chart illustrating an exemplary embodiment of theprocessing steps involved in call-waiting as implemented by theprocessing elements of FIG. 3;

FIG. 5 is a block diagram illustrating an exemplary hard handoffscenario in a cellular telephone system;

FIG. 6 is a state diagram illustrating the states of a mobile station ina mobile station terminated call;

FIG. 7 is a block diagram illustrating an exemplary embodiment of thehard handoff scenario according to the present invention;

FIG. 8 is a flow chart illustrating an exemplary embodiment of theprocessing steps involved in hard handoff as implemented by theprocessing elements of FIG. 3;

FIG. 9 is a block diagram illustrating an exemplary embodiment of theprocessing elements involved in the resolution of a glare condition; and

FIG. 10 is a flow diagram illustrating the occurrence and the resolutionof a glare condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exemplary CDMA cellular mobile telephone system in which the presentinvention is embodied is illustrated in FIG. 1. The CDMA cellulartelephone system is indicated generally by 9 and includes a mobileswitching center (MSC) 10, also referred to as a mobile telephoneswitching office (MTSO), that includes interface and processingcircuitry for providing system control to the base stations. The MSC 10routes telephone calls from a public switched telephone network (PSTN)11 to the appropriate base station for transmission to the appropriatemobile station. The MSC 10 also controls the routing of calls from themobile stations via one or more base stations to the PSTN 11. Inaddition, the MSC 10 may direct calls between mobile stations via theappropriate base stations. The MSC 10 may be coupled to the basestations by various conventional means, such as dedicated telephonelines, optical fiber links, or by radio frequency communications.

It should be understood that although the present invention is describedherein within the context of a CDMA cellular communications system, itis equally applicable to other types of communication systems, such asthe personal communication system (PCS). Furthermore, systems utilizingother well known transmission modulation schemes such as TDMA and FDMAas well as other spread spectrum systems may employ the presentinvention.

In FIG. 1, two exemplary base stations (BSs), 12 and 14, along with twoexemplary mobile stations (MSs) 16 and 18, each including a cellulartelephone, are illustrated. Arrows 20 a and 20 b represent forward andreverse code channels that define a possible communication link betweenBS 12 and MS 16. Arrows 22 a and 22 b define a possible communicationlink between BS 12 and MS 18. Similarly, BS 14 can establish a two-waycommunication link with MS 18 as represented by arrows 24 a and 24 b andwith MS 16 as represented by the arrows 26 a and 26 b.

As previously mentioned, the interface between BSs 12 and 14 and MSs 16and 18 is called the Air-Interface, and in the exemplary embodiment,call processing on the Air-Interface is governed by IS-95-A. Also aspreviously mentioned, the interface between MSC 10 and BSs 12 and 14 iscalled the A-Interface, and call processing on the A-Interface isgoverned by IS-634. The present invention recognizes that theA-Interface as currently defined by IS-634 lacks support for some of thenecessary functionality for reliable call processing. In addition, thepresent invention recognizes that introduction of a new message on theA-Interface will cure some of the deficiencies of the A-Interface.

An exemplary procedure in which deficiencies are recognized on theA-Interface is the call waiting procedure. Call waiting is one featureavailable to the CDMA cellular subscriber. The call waiting featureallows a cellular subscriber to toggle between two parties on thetelephone network. Call waiting may be provided in a CDMA telephonesystem according to the techniques disclosed in copending U.S. patentapplication Ser. No. 08/535,998, entitled “Early Detection of Mobile toMobile,” filed Sep. 29, 1995, which is assigned to the assignee of thepresent invention and incorporated by reference herein.

An exemplary call waiting scenario is illustrated in FIG. 2. In FIG. 2,party 1 28 and party 2 30 are two parties of a PSTN. A call has beenestablished between MS 32 and party 1 28. A traffic channel has been setup between MS 32 and BS 34 on the Air-Interface. Furthermore, BS 34 isconnected to MSC 36 on the A-Interface by any of various conventionalmeans as described above.

If party 2 30 calls MS 32 while MS 32 is communicating with party 1 28,MSC 36 will send signaling data to BS 34 indicating that another partyis attempting to contact MS 32. The means for combining traffic data andsignaling data is described in detail in U.S. Pat. No. 5,511,073,entitled “METHOD AND APPARATUS FOR THE FORMATTING OF DATA FORTRANSMISSION,” assigned to the assignee of the present invention andincorporated by reference herein. To inform MS 32 that another call iscoming in, an alerting signal is relayed by BS 34 to MS 32 either by aFlash With Information message or an inband tone. Then, MS 32 can invokethe call waiting feature by pushing a specific key on the MS keypad.This causes the generation of a Flash With Information Message, which issent on the Air-Interface to BS 34, which in turn relays the Flash WithInformation Message on the A-Interface to MSC 36. MSC 36 then connectsparty 2 30 to MS 32 while putting party 1 on hold. Thereafter, MS 32 maytoggle between party 1 28 and party 2 30 by pushing the key on thekeypad to cause the generation of the Flash With Information Message.Each time MSC 36 receives the Flash With Information Message, itconnects MS 32 to the party that was previously put on hold and puts onhold the party that was previously on the line.

Referring still to FIG. 2, assume that party 1 28 is on hold and MS 32is connected to party 2 30. If party 2 30 hangs up, then according tothe current procedure, the network which is servicing party 2 generatesa Release Message. This Release Message propagates to MSC 36, which thensends the Release Message to BS 34 on the A-Interface. BS 34 in turnsends a Release Message to MS 32 on the Air-Interface to cause MS 32 torelease its traffic channel. MSC 36 then signals to BS 34 that party 128 is attempting to contact MS 32. This causes BS 34 to send a Pagingmessage to MS 32 to indicate that a call is incoming. In response, MS 32generates a Paging Response Message which is transmitted to BS 34. BS 34then transmits the Paging Response Message to MSC 36. On receipt of aPaging Response Message, MSC 36 assigns a new traffic channel to MS 32and MS 32 is reconnected to party 1 28.

The present invention recognizes that this procedure has severalshortcomings. First, it does not efficiently use the Air-Interfaceresource, since it requires the release of the traffic channel,re-paging of MS 32 and the assignment of a new traffic channel. Further,the need to obtain a new traffic channel makes it difficult toreestablish the connection between MS 32 and party 1 28. If MS 32 movesaway from BS 34 from which it is released, the page from MSC 36 may notbe received by MS 32. At the very least, this increases the amount oftime that party 1 28 has to wait for the reconnection with MS 32. Thereis also the possibility that the connection between MS 32 and party 1 28cannot be reestablished, resulting in a dropped call. A better procedureis needed to handle the procedure for releasing party 2 30 from MS 32wherein MS 32 is using the call waiting feature.

To overcome the shortcomings, the present invention introduces a newmessage for the A-Interface. A preferred embodiment of the presentinvention is illustrated in FIG. 3. The preferred embodiment providesfor a new message, an Alert With Information Message, on theA-Interface. The Alert With Information Message is currently availableon the Air-Interface under IS-95-A. According to IS-95-A, the Alert WithInformation Message is sent by a base station to a mobile station tocause the mobile to ring and to transition from a Conversation State toa Waiting For Answer State, expecting the mobile user to intervene. Byproviding for an Alert With Information Message on the A-Interface, themobile switching center can better control the progress of the callwaiting procedure.

Referring to FIG. 3, assume again that party 1 28 is on hold and MS 32is in communication with party 2 30. If party 2 30 then hangs up, thenetwork servicing party 2 30 generates a Release Message as describedabove. In the preferred embodiment, when the Release Message comes fromthe network, MSC 36 intercepts it, and message generator 38 in MSC 36generates an Alert With Information Message signal, which is sent to BS34 on the A-Interface. Message receiver 40 in BS 34 receives the AlertWith Information Message, and BS 34 in turn sends an Alert WithInformation Message to MS 32 on the Air-Interface. When MS 32 receivesthe Alert With Information Message, it generates an alerting signal inthe mobile and waits for the subscriber to answer. When the subscriberanswers by pressing a key on keypad of MS 32, a Connect Messagegenerated by MS 32 is sent to BS 34 and forwarded to MSC 36. Onreceiving the Connect Message, MSC 36 connects party 1 28 to MS 32.

In the preferred embodiment, by not permitting the Release Message (or aClear Message) from the network to be sent to MS 32, MS 32 is not causedto release the traffic channel when party 2 30 hangs up. As a result,there is no need to expend additional Air-Interface resources for theassignment of a new traffic channel. Furthermore, the preferredembodiment does not require MS 32 to be paged following the release ofthe traffic channel to indicate that party 1 28 is still waiting to bereconnected with MS 32. Consequently, the risk that MS 32 will move awayfrom the coverage area of BS 34 and not receive the page is eliminated.

A brief illustration of the steps involved in call waiting as describedin the embodiment above is shown in FIG. 4. FIG. 4 shows a flow chartillustrating some of the steps involved in the processing as discussedwith reference to FIG. 3.

Another procedure in which deficiencies are recognized on theA-Interface is the handoff procedure. In a cellular communicationsystem, a handoff must take place when a mobile station moves from thecoverage area of one base station to another base station. A geographicarea in a cellular system is divided up into cells. Each cell isserviced by a corresponding base station. In a hard handoff environment,as a mobile station moves from one cell to another cell, communicationwith the original base station is terminated before communication withthe subsequent base station is established. In a soft handoffenvironment, communication with the subsequent base station isestablished before terminating communication with the original basestation. U.S. Pat. No. 5,267,261, which is incorporated by reference andassigned to the assignee of the present invention, discloses a methodand system for providing soft handoff.

The hard handoff procedure in a mobile terminated call may be understoodwith reference to FIGS. 5 and 6. As illustrated in FIG. 5, as MS 42moves from the coverage area of BS1 44 to BS2 46, a connection needs tobe established between MS 42 and BS2 46 while MS 42 needs to bedisconnected from BS1 44. Both BS1 44 and BS2 46 are shown to beconnected to MSC 48 in FIG. 5. However, it should be understood that ahard handoff can also occur when a mobile station moves from the controlof one mobile switching center to another. In fact, the different mobilestation controllers may support different modulation techniques such asTDMA or FDMA.

In FIG. 6, the states of a mobile station in a mobile terminated callare briefly illustrated. The states are summarized herein and explainedmore fully in the aforementioned document IS-95-A, pages 6-160 to 6-161.

The progression of the hard handoff procedure is dependent on the stateof the mobile station. Referring to FIG. 6, in a mobile stationterminated call, the mobile is in the Traffic Channel InitializationState, shown by block 50, when a traffic channel has been establishedbetween a mobile station and a base station. Upon receipt of a BaseStation Acknowledgment Order from the base station, the mobile movesinto the Waiting For Order State, shown by block 52. The mobile stationthen transitions into the Waiting For Answer State, illustrated by block54, when it receives an Alert With Information Message from the basestation. When the mobile station subscriber answers the call by pushinga specific key on the mobile station keypad, the mobile transitions intothe Conversation State, represented by block 56. The mobile transitionsinto the Release State, shown by block 58, when conversation terminates.

According to the current procedure, a mobile station should be in theWaiting For Answer State 54 or the Conversation State 56 during hardhandoff. If the mobile is in any other state, the call is likely to bedropped during hard handoff. Thus, the mobile station must receive anAlert With Information Message transmitted by the base station on theAir-Interface before the mobile station undertakes handoff. Otherwise,the handoff procedure would be unreliable. Referring again to FIG. 5,assume that MS 42 is in the coverage area of BS1 44. If MS 42subsequently moves from the coverage area of BS1 44 to the coverage areaof BS2 46 while MS 42 is in the Waiting For Order State 52, MS 42 maynot receive the Alert With Information Message sent by BS1 44. Withoutreceiving the Alert With Information Message, MS 42 cannot transitioninto the Waiting For Answer State 54 in the coverage area of BS2 46. Asa result, the call will be dropped while handoff is in progress. Thus,the present invention recognizes that a better method for handling hardhandoff in a mobile station terminated call is necessary.

As previously described, providing an Alert With Information Message onthe A-Interface overcomes the shortcomings in the call waitingprocedure. The present invention recognizes that providing an Alert WithInformation Message on the A-Interface will also overcome theshortcomings in a hard handoff procedure in a mobile station terminatedcall. Further, it should be understood that the present inventionapplies to hard handoff procedures in a variety of communicationenvironments, including CDMA, TDMA, or FDMA.

A preferred embodiment of the use of an Alert With Information Messageon the A-Interface in a hard handoff procedure is illustrated in FIG. 7with reference to FIG. 6. An Alert With Information Message is generatedby message generator 50 in MSC 48 and sent to message receiver 52 in BS246. The Alert With Information Message is sent on the A-Interface whenMS 42 is moving from the coverage area of BS1 44 to the coverage area ofBS2 46 while in the Waiting For Order State. After BS2 46 receives theAlert With Information Message from MSC 48, BS2 46 then sends an AlertWith Information Message to MS 42 on the Air-Interface. Having receivedthe Alert With Information Message, MS 42 can transition into theWaiting For Answer State 54 while in the coverage area of BS2 46, andhandoff can occur without the call being dropped. Thus, by providing foran Alert With Information Message on the A-Interface, MSC 48 has bettercontrol of the hard handoff procedure. Since MSC 48 can send the AlertWith Information Message to BS2 46, causing BS2 46 to send the AlertWith Information Message to MS 42, MS 42 does not need to rely onreceiving the Alert With Information Message from BS1 44 in order totransition into the Waiting For Answer State 54. Consequently, handoffcan occur without the call being dropped. A flow chart illustrating someof the processing steps involved in hard handoff as described in theembodiment above is shown in FIG. 8.

Still another procedure in which deficiencies are recognized on theA-Interface is the handling of a glare condition. A glare condition iswhen a mobile subscriber attempts to initiate a call while another partyis attempting to call the mobile subscriber. A call initiated by amobile subscriber is referred to as a mobile station originated call,while a call made to a mobile subscriber is referred to as a mobilestation terminated call.

The glare condition may be better understood by referring back to FIG.1. In a mobile station originated call, an Origination Message istransmitted from a mobile station, such as MS 16, to a base station,such as BS 12, upon initiation of a call by MS 16. After transmission ofthe Origination Message but before a connection is established betweenMS 16 and the called party (party A of PSTN 11), another party (party Bof PSTN 11) may attempt to contact the mobile subscriber and MSC 10 maypage MS 16, causing in a glare condition. The Air-Interface standard,IS-95-A, permits MS 16 the option of aborting the call to party A andresponding to the call from party B. MS 16 then follows the statetransition sequence for a mobile station terminated call as illustratedin FIG. 6.

Referring now to FIG. 6, in a mobile station termination scenario, themobile expects to receive an Alert With Information Message totransition from the Waiting For Order State, represented by block 52, tothe Waiting For Answer State, represented by block 54. If the Alert WithInformation Message is not received, the mobile would time out andrelease the call.

It is recognized by the present invention that current procedures underIS-95-A and IS-634 do not properly resolve the glare condition.Currently, the base station is not configured to transmit an Alert WithInformation Message to the mobile station upon occurrence of a glarecondition. The problem is explained in greater detail with reference toFIG. 9. Referring to FIG. 9, when MS 60 originates a call, anOrigination Message is sent from MS 60 to BS 62. In response to theOrigination Message, BS 62 transmits a BS Acknowledgment Order to MS 60.Meanwhile, MSC 64 receives an incoming call to the same MS 60, unawareof the origination effort in progress, and sends a Paging RequestMessage to BS 62 to initiate a mobile terminated call setup. BS 62 inturn sends a Page Message containing the MS address, and the PageMessage is received by MS 60.

Due to the mobile origination attempt, BS 62 constructs a ServiceRequest Message and sends the message to MSC 64. However, afterreceiving the Page Message, MS 60 aborts the origination call setup, andresponds by transmitting a Paging Response Message, which is received byBS 62. But because MSC 64 had received a Service Request Message from BS62, MSC 64 in response sends an Assignment Request Message to BS 62,requesting assignment of Air-Interface resources for the mobile stationoriginated call. Upon receipt of the Assignment Request Message, BS 62assumes that a mobile station originated call is in progress, and doesnot transmit an Alert With Information Message to MS 60. As a result, MS60 times out waiting for the Alert With Information Message, and themobile station terminated call is dropped.

In order to better resolve the glare condition, the present inventionprovides for still another use of the Alert With Information Message onthe A-Interface. First, note that after BS 62 receives a Paging ResponseMessage from MS 60, BS 62 in turn sends a Paging Response Message to MSC64. Then, in a preferred embodiment, the present invention provides foran Alert With Information Message to be transmitted on the A-Interfaceif MSC 64 receives a Service Request Message and then a Paging ResponseMessage. Still referring to FIG. 9, it can be seen that the Alert WithInformation Message may be generated in MSC 64 by message generator 66,while the Alert With Information Message may be received in BS 62 bymessage receiver 68. After BS 62 receives the Alert With InformationMessage from MSC 64, BS 62 then sends an Alert With Information Messageto MS 60 on the Air-Interface. Having received the Alert WithInformation Message, MS 60 can transition into the Waiting For AnswerState, and the glare condition is resolved without the call beingdropped.

Referring now to FIG. 10, a flow chart illustrating some of theprocessing steps involved in the resolution of the glare condition asdiscussed with reference to FIG. 9 is shown. An Alert With InformationMessage is provided on the A-Interface to resolve the glare condition.

The present invention recognizes that for the call waiting, hardhandoff, and resolution of a glare condition procedures, there arecertain deficiencies in call processing on the A-Interface as currentlydefined by IS634. By providing an Alert With Information Message on theA-Interface, the present invention overcomes these deficiencies. TheAlert With Information Message is already available on the Air-Interfaceunder IS-95-A to cause a mobile station to transition from the WaitingFor Order State to the Waiting For Answer State. An Alert WithInformation Message is provided on the A-Interface to trigger thetransmittal of the Alert With Information Message on the Air-Interface,solving the problems of the call-waiting and handoff procedures as wellas resolving the glare condition.

The previous description of the preferred embodiments is provided toenable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

1. A CDMA cellular telecommunications messaging system, comprising: amessage generator in a mobile switching center for generating an IS-634message signal, said message signal for transmission to a base stationfor triggering said base station to transmit a subsequent message signalto a mobile station; and a message receiver in said base station forreceiving said message signal; wherein said message signal is generatedupon detection by said mobile switching center of a condition whereby amobile subscriber attempts to originate a call while another party isattempting to call the mobile subscriber; wherein said condition isdetected when said mobile switching center receives a message indicativeof a mobile station originated call and a message indicative of saidmobile station terminated call in quick succession; and wherein saidmessage signal is generated in response to the receipt of a ReleaseMessage by said mobile switching center, said Release Message havingbeen generated by a network servicing a party which is to terminate itsconnection with said mobile station, said party being one of two partiescommunicating with said mobile station in a call waiting procedure. 2.The messaging system of claim 1 wherein said message indicative of saidmobile station originated call is a Service Request Message and saidmessage indicative of said mobile station terminated call is a PagingResponse Message.
 3. The messaging system of claim 1 wherein saidmessage signal is an Alert With Information Message signal and saidsubsequent message signal is an Alert With Information Message signal.4. The messaging system of claim 2 wherein said message signal is anAlert With Information Message signal and said subsequent message signalis an Alert With Information Message signal.
 5. A CDMA cellularcommunication system, comprising: a mobile station; a base station incommunication with said mobile station via an Air-Interface, said basestation defining a first cellular coverage area; a mobile switchingcenter in communication with said base station via an IS-634A-Interface; a message generator at said mobile switching center forgenerating a message signal for transmission to said base station onsaid A-Interface; a message receiver at said base station for receivingsaid message signal, wherein upon receipt of said message signal, saidbase station transmits a subsequent message signal to said mobilestation on said Air-Interface; a first party in a first network; asecond party in a second network, said first and second parties being incommunication with said mobile station in a call waiting procedure,wherein said second network generates a Release Message indicative ofthe termination of communication of said second party with said mobilestation, said Release Message being transmitted to said mobile switchingcenter to cause said mobile switching center to generate said messagesignal; wherein said message generator generates said message signalwhen said mobile switching center detects a condition whereby a mobilesubscriber attempts to originate a call while another party isattempting to call the mobile subscriber.
 6. The cellular communicationsystem of claim 5 wherein said message signal is an Alert WithInformation Message signal and said subsequent message signal is anAlert With Information Message signal.
 7. The cellular communicationsystem of claim 5 wherein said condition is detected when said mobileswitching center receives a message indicative of said mobile stationoriginated call and a message indicative of said mobile stationterminated call in quick succession.
 8. The cellular communicationsystem of claim 7 wherein said message indicative of mobile stationoriginated call is a Service Request Message and said message indicativeof said mobile station terminated call is a Paging Response Message. 9.The cellular communication system of claim 8 wherein said message signalis an Alert With Information Message signal and said subsequent messagesignal is an Alert With Information Message signal.
 10. In a CDMAwireless communication system, a method for messaging between a mobileswitching center and a base station, comprising: detecting theoccurrence of a condition whereby a mobile subscriber attempts tooriginate a call while another party is attempting to call the mobilesubscriber; generating a message signal in said mobile switching centerbased on a positive result of said detecting; transmitting said messagesignal to said base station on an IS-634 A-Interface, wherein uponreceipt of said message signal, said base station transmits a subsequentmessage signal to a mobile station on an Air-Interfaces; establishingcommunication between a first party and said mobile station via saidmobile switching center and said base station; establishingcommunication between a second party and said mobile station via saidmobile switching center and said base station while putting said firstparty on hold; and generating a Release Message in a network servicingsaid second party to indicate that the second party is terminatingcommunication with said mobile station, said Release Message transmittedto said mobile switching center, wherein said message signal isgenerated responsive to receipt of said Release Message by said mobileswitching center.
 11. The method of claim 10 wherein said detectingcomprises: determining if a message indicative of said mobile stationoriginated call is received at said mobile switching center; anddetermining if a message indicative of said mobile station terminatedcall is received at said mobile switching center.
 12. The method ofclaim 11 wherein said message indicative of a mobile station originatedcall is a Service Request Message and said message indicative of saidmobile station terminated call is a Paging Response Message.
 13. Themethod of claim 12 wherein said message signal is an Alert WithInformation Message signal and said subsequent message signal is anAlert With Information Message signal.
 14. An apparatus of a CDMAwireless communication system, comprising: means for detecting anoccurrence of a mobile subscriber attempting to originate a call whileanother party is attempting to call the mobile subscriber; means forgenerating a message signal in a mobile switching center based on apositive result of said detecting; means for transmitting said messagesignal to a base station on an IS-634 A-Interface, wherein upon receiptof said message signal, said base station transmits a subsequent messagesignal to a mobile station on an Air-Interface; means for establishingcommunication between a first party and said mobile station via saidmobile switching center and said base station; means for establishingcommunication between a second party and said mobile station via saidmobile switching center and said base station while putting said firstparty on hold; and means for generating a Release Message in a networkservicing said second party to indicate that the second party isterminating communication with said mobile station, said Release Messagetransmitted to said mobile switching center, wherein said message signalis generated responsive to receipt of said Release Message by saidmobile switching center.
 15. The apparatus of claim 14 wherein saidmeans for detecting comprises: means for determining if a messageindicative of said mobile station originated call is received at saidmobile switching center; and means for determining if a messageindicative of said mobile station terminated call is received at saidmobile switching center.
 16. The apparatus of claim 15 wherein saidmessage indicative of a mobile station originated call is a ServiceRequest Message and said message indicative of said mobile stationterminated call is a Paging Response Message.
 17. The apparatus of claim16 wherein said message signal is an Alert With Information Messagesignal and said subsequent message signal is an Alert With InformationMessage signal.